Within a generator rotor, windings need to be electrically insulated from the rotor body. This is accomplished by lining the slots into which the windings are placed with insulation. The insulation is referred to as slot cells and they essentially form a receptacle within a rotor body slot where the windings are placed.
FIG. 1 illustrates a close up view of windings 2 within a slot 4 of a rotor body 6. The rotor body 6 has a series of radial/axial slots 4 into which the windings 2 are placed. The slot cell 8 insulation is placed along the length of the slots 4 and it axially extends from the end of the slot about 1.5 inches (3.75 cm). This is because the slot cells can slide, also referred to as migrate, during operation of the rotor. If the windings 2 come into direct contact with the rotor body 6 a ground path is created which causes considerable damage to the generator core.
The slot cells are typically either of a single U-shaped piece or two L-shaped pieces. The additional extension of the slot cells to either end of the rotor body slots allows for some migration of the slot cells during operation. However, the migration of the slots cells still has to be closely monitored and the risk of creating a ground through contact of the windings with the rotor body is always present.
What is needed is a method and apparatus that prevents migration of the slot cells without interfering with the normal function of a generator rotor.